Graeme Archer works as a statistician, and is a winner of the Orwell Prize for Political Blogging. He writes a column in Saturday's Daily Telegraph.

Why is the murder of Bijan Ebrahimi so terrifying?

Last week I wrote a piece about the murder of Bijan Ebrahimi. I looked at it, and decided not to file it. I didn't trust the strength of my reaction; perhaps I was being too emotional. Maybe it's wrong to stare too hard, head-on, at evil. Most of the world isn't like that.

Without retreading the points these fine writers make, or using the murder as a political tentpole, let us dissect the anatomy of the horror. Because – one truth – is that I feel shame at not filing the piece. Writing isn't cathartic unless it acts as witness. Why does the lynch mob cause the blood to chill? I think you know the answer to that.

Here's one of Mr Ebrahami's "neighbours", if we can abuse language sufficiently to use that term:

On the Thursday evening (before his death) everyone came out and they were calling him a paedophile. There were about 20 people out there all having a say. They had him down as a 100 per cent paedophile.

As opposed to, say, an 80 per cent paedophile? A 23 per cent one? The forensic ability of this "everyone" is a scientific wonder.

Here's a statement from the local constabulary, made after Mr Ebrahimi's murderers confessed their guilt in court:

Mr Ebrahimi was arrested on suspicion of a public order offence – breach of the peace – and after being interviewed he was released with no further action taken. We can categorically state he had not taken any indecent images and that nothing of concern had been found on his computer.

"No further action taken": not by the police, anyway.

So, would this be an accurate summary? Vandals damage a man's garden. He photographs this. His "neighbours" object, and make up entirely spurious accusations. The innocent man is then arrested by the police for breaching the peace (by complaining about the vandalism? or the made-up accusations?) removed to a police station, then released back to the hands of the mob, which kills him.

The IPCC has started an investigation into the behaviour of the police officers involved. Avon and Somerset police said: "…we’re working with the IPCC to support them in whatever way we can as they carry out their investigation. In the meantime, we hope Mr Ebrahimi’s family can draw some comfort from the fact that the two men involved in his murder have pleaded guilty." Best not to add any comment to this. For now.

Meanwhile, here are the lessons for the rest of us. Don't live on your own. Don't care for your garden, or for your cat. Don't object when children treat you like s–––. Such activities are an invitation to the bully, who's prowling the streets outside your home and sniffing for weakness like a hound with a taste for blood. Show that you care about anything, and you show him how to hurt you.

You know why the death of Bijan Ebrahimi is so terrifying, don't you? The next mob might turn itself on you. Don't, should the bully single you out, raise your voice in anger. This might constitute a breach of the peace. No further action will be taken.